In the communications tower industry, guyed towers are supported by one or more levels of braided or stranded high-strength steel guy cables that anchor the structure to the ground. Maintenance of guyed towers requires the guy cables to be inspected for proper tension. Proper tension ensures that the tower is correctly supported and that there is minimal deflection of antennas caused by twisting of the tower.
It is often necessary to ascertain the tension value of stressed cables in a quick, reliable manner without permanent attachment of the measuring device thereto.
Devices for measuring tension in a given length of stressed cable are known in the art. Such devices are used to determine tension in stressed cables by measuring the fundamental frequency or vibration thereof and utilizing this value to represent cable tension (U.S. Pat. No. 3,540,271).
Another prior art device (U.S. Pat. No. 4,158,962) provides a method and apparatus for measuring tension in a cable which involves affixing a small permanent magnet to the cable, imparting a disturbance to the cable thereby causing the cable and the magnet to vibrate, then detecting the frequency of alternating current or magnetic field perturbation caused by vibrations. An electrical signal is generated by sensing the fluctuating field of the permanent magnet attached to the vibrating cable and generating from this signal a periodic pulse signal having an average level proportional to the square of the cable variation frequency. The resulting signal is scaled to produce a final signal which is directly proportional to cable tension.
Another prior art device (U.S. Pat. No. 4,565,099) measures the tension in a suspended cable or similar material, wherein the tension is derived from sensor signals corresponding to the fundamental frequency of vibration in the cable. Such a device measures tension from sensors located at or near the terminal end point of a span of cable.
Prior art devices for measuring tension in a given length of stressed cable are bulky, cumbersome, expensive, and difficult to maintain because the instrumentation and meter used for measuring the tension of a stressed cable are attached to the tension measuring device by connecting wires. Such devices are difficult to use in inclement weather and require weather proofing for each individual component. In addition, such devices are not well-suited for use in the industry as they are not easily portable.
The term “cable”, as used herein, includes rope, wire, chain, line, strand, lead, filament, or cord, in braided, coiled, single or multiple strands, or any similar structure which essentially functions in the same manner as a cable.